This application claims the priority of German application 197 34 426.7, filed in Germany on Aug. 8, 1997 and German application 198 25 906.9, filed in Germany on Jun. 10, 1998, the disclosures of which are expressly incorporated by reference herein.
The present invention relates to a rotor cup for open-end spinning aggregates comprising a rough-surfaced fiber collecting groove in relation to the fibers to be spun, which fiber collecting groove is provided with a nickel plating containing diamond grains, said rotor cup also comprising a smooth fiber sliding surface in relation to the fibers, which is provided with a nickel plating without diamond grains.
German published patent application 43 05 626 discloses that the fiber collecting groove, in relation to the fibers, should have a greater friction resistance than the fiber sliding surface. This, on the one hand, permits the fibers to slip sufficiently easily into the fiber collecting groove in the case of relatively steep fiber sliding surfaces of spinning rotors with small diameters, while on the other hand it is ensured that the fibers take on the circumferential speed of the spinning rotor at the latest at the fiber collecting groove. All the surfaces of the rotor cup are completely covered with a nickel-diamond plating. The desired roughness in the fiber collecting groove comes about in the known spinning rotor in that individual diamond grains project out from the plating. The fiber sliding surface is, in contrast, subsequently smoothed, whereby a large percentage of the diamond grains are pulled out, by means of which the fiber sliding surface loose the undesired gripping effect. This method has a disadvantage in that costly diamond particles are applied to the entire surface of the rotor cup and then subsequently removed, at least on the area of the fiber sliding surface, as their function is not required in this area.
It is an object of the present invention to plate a rotor cup of the above mentioned type in such a way that from the very beginning, diamond particles are applied only where they are actually required.
This object has been achieved in accordance with the present invention in that two nickel platings are applied in two separate plating processes.
As it was assumed up to now that it was not possible to provide only the fiber collecting groove with a nickel-diamond plating, as the plating process is applied in a single bath, the process according to the present invention nevertheless enables the diamond particles to be applied only in the fiber collecting groove. It is hereby practical when the diamond grains of the nickel plating on the fiber collecting groove have a grain size of 4 .mu.m.
For the purpose of the present invention, the plating process is carried out in the following stages:
Firstly, the entire rotor cup is chemically nickel-plated, whereby the desired plating is created on the fiber sliding surface, and a corrosion protection is created on all surfaces of the rotor cup, also on parts which the fibers do not actually reach. Next, the fiber collecting groove is covered with a removable insert, which is designed, for example, as an elastically flexible plastic mask. Thereafter, the entire rotor cup can be lowered into a bath of protective coating, for example, liquid wax, whereby the removable insert prevents the protective coating from entering the fiber collecting groove. When the insert is removed from the fiber collecting groove, the entire remaining contour of the rotor cup, already nickel-plated, is covered with a protective coating. Thus the rotor cup can now be provided with a nickel-diamond plating in a bath, whereby this nickel-diamond plating is applied only to the fiber collecting groove, namely on the already present, previously applied nickel plating. Thus the costly diamond particles are only applied where they are later actually required. When finally the protective coating is removed from the remaining contours of the rotor cup, the result is a rotor cup in which the fiber collecting groove is provided with a rough nickel-diamond plating and the fiber sliding surface is provided with a smooth, purely nickel plating. As the nickel plating also covers the outer contours of the rotor cup, additional protection against corrosion is achieved.
The nickel plating need not, of course, consist of pure nickel; a nickel alloy is also possible in this case.